There are two well-standardized tests in common use to confirm a reactive result of a screening test for syphilis (Rapid Plasma Reagin, RPR); these are the flourescent-treponemal antibody (FTA-ABS) and microhemagglution (MHA-TP). Most published reports indicate that the MHA-TP test is at least as specific as the FTA-ABS test for routine diagnostic purposes, but is less sensitive in primary syphilis. It has also been noted that in patients with autoimmune disorders, 15% showed some degree of fluorescence in the FTA-ABS test while no clinical evidence of syphilis could be documented. Analyzing our 1982 NIH experience, 100 reactive sera were found by RPR from a total of 2000 sera. Among these 100 reactive sera, 62 were positive by the FTA-ABS test. Fourteen patients (22%) had underlying autoimmune disorders with no evience of syphilis. The goal of this study is to compare the specificty of the MHA-TP and FTA-ABS tests.